Fire damp proof explosive compositions



the corresponding explosives.

2,829,036 Patented Apr. 1, 1958 FIRE DAMP-PROOF EXPLOSIVE COIVIPOSITIONSAdolf Berthmann, Leverlrusen-Schlebusch, and Gotthard Kuhn, Leverkusen,Germany, assignors to Dynamit Aktiengesellschaft vormals Alfred Nobel &Co., Troisdorf, near Cologne, Germany No Drawing. Application March 3,1954 Serial No. 413,944

Claims priority, application Germany March 7, 1953 9 Claims. (CI. 52- 7)and an equivalentproportion of potassium nitrate or sodium nitrateexhibit a high degree of safety against firedamp. In addition, thechlorine in the ammonium chloride should be completely takenup by thepotassium or sodium present, so that the vapours evolved should containno free hydrochloric acid. However, since quite different standards wereimposed at that time on the safety of explosives against firedamp, theexplosives then considered safe scarcely conform to the conditions ofpresent-day permitted explosives.

A method based upon the disclosure of the aforesaid patent has recentlybeen applied because such explosives have less tendency to'hardenand-agglomerate in storage than the explosives hitherto employed. It hasbeen found that the firedamp safety thus obtained does notsubstantia'lly exceed the limits of that hitherto obtained.

It has now been found possible to produce firedamp proof explosivescomprising a mixture of alkali nitrate and ammonium chloride capable ofreacting together to form an alkali chloride and a highly sensitiveexplosive component, in which the grain fineness of the two salts issuch that the proportion of the highly sensitive component in saidexplosives can be made larger than the corresponding proportionshitherto used in such explosives. The explosive power or detonation ofthese new explosives is consequently alsogreater than that of Almost allpermitted explosives contain a highly sensitive component generallynitroglycerine and nitroglycol, in addition to diglycol dinitrate, ordinitrochlorhydrin, or a mixture of a number of blasting oils or solidexplosives, such for example as nitropentaerythritol, which to someextent represent the carrier of the detonation and must be present insuch quantity that the propagation of the detonation in the explosiveitself and the transmission the ammonium ion with the nitrate ion in thepair of salts takes place so slowly, in contrast to what happens in thedetonation of the highly sensitive component, that this energy-supplyingreaction does not substantially increase the detonation shock, but onlyprolongs it. This difference in the speed of reaction is believed toresult from the fact that, in the highly sensitive component, the

oxygen and the combustible hydrogen and carbon containing compound arepresent in the same molecule, while, in the pair of reactive salts, theoxygen in the sodium nitrate crystals is present separately from thecombustible substance, i. e. the sal ammoniac crystals. ,The' latterre-.

action is therefore partly dependent upon the grain fineness of thenitrate and of the sal ammoniac and the reaction of the salts in thedetonation can consequently be controlled by their grain fineness. Ithas been found that, since the pair of salts must be present in a grainfineness which is particularly favourable [for firedamp safety andpower, the proportion of the highly sensitive component depends in turnupon this grain fineness of the salts;

It has also been found that the maximum firedamp safety is obtained withoptimum explosive power if, when employing the pair of salts, ammoniumchloride and sodium nitrate, a grain fineness is.chosen such that atleast 20% and at most 90% of said salts will pass through the GermanIndustrial Standards sieve No. 60. The quantity of highly sensitivecomponent must in this case be be-- tween 7 and 12%. By conforming tothese conditions, it is possible to increase the lead block expansionwhile maintaining their permitted degree of firedamp safety.

If, for example, sodium nitrate of which 32% is finer than 0.1 mm., andammonium chloride of which 22% is finer than 0.1 mm., are employed and astoichiometric mixture is'prepared therefrom, 7% of blasting oil isnecessary in order to produce an explosive having a good detonatingaction, with a good firedamp safety.

However, if, for example, a mixture of equivalent quantities of ammoniumchloride and sodium nitrate is employed instead of the said salts,sodium chloride is formed by double decomposition in addition toammoniumnitrate. This sodium chloride, in contrast to sodium chloride Which isadded as such to the explosive, is present in a substantially morefinely distributed state, and has been found to increase the firedampsafety of the explosive in which it is produced. r

It is believed that the energy-supplying reaction of If the quantity ofblasting oil is increased to 8% and: more, the safety against firedampis considerably decreased. If sodium nitrate and ammonium chloride areused, of which is below 0.1 mm., an addition of 10.5% of blasting oilwill still allow a safe transmission of the detonation, while with agrain fineness of 94% below 0.1 mm., an addition of 13.5% of blastingoil is necessary for transmission. However, it is found that, with thislast increased addition of blasting oil, the optimum firedamp safetyis'no longer afforded.

In the said pair of salts, the ammonium chloride may be replaced byother chlorine-containing substances which are not salts but which reactwith the sodium nitrate present and thereby generate gas and heat. Inall cases, the quantity of sodium nitrate present must be at leastsufficient to combine with all the chlorine evolved during the reaction.Such chlorine-containing substances are, for example,hexachlorocyclohexane or dinitrochlorhydrin, the latter also beingcapable of simultaneously performing the function of the highlysensitive component.

The systemshitherto mentioned, which form sodium chloride by an internalreaction, are the most favourable with regard to the vapours evolved,since the sodium chloride which is in the form of a thick fog does notproduce any irritation of the respiratory pas-sages. Alternatively, thesodium nitrate may be entirely or partially replaced by other nitrates,particularly of metals chosen from Group Ia or 11a of MendeleefsPeriodic Table of the Elements, such as potassium or calcium.

Instead of the chlorineacontaining substances, carboncontaining andhydrogen-containing salts such as ammonium oxalate or sodiumacetate,'which form sodium carbonate with the nitrate present, may beemployed. Organic substances such as wood meal, urea and guanidinenitrate may also be employed. In all such cases,

U the grain fineness of the reacting substances and the quantity ofhighly sensitive explosive component are so adapted to one another thatthe optimum firedamp safety and explosive-force are obtained.

In addition to the reactive substances, inert substances may also beadded, as in the case of the known permitted explosives.

The foregoing invention is now illustrated by the following examples:

Example 1 Nitroglycerine "percent" 4.2 Nitroglycol do 2.8 Argillaceousearth do 0.5 Sodium nitrate, 32% finer than 0.1 mm. do 56.8

Ammonium chloride, 22% finer than 0.1 mm.

percent 35.7

Lead block expansion cc 79 Detonation transmission with a cartridgediameter of 32 mm. cm 15 Safety against methane-air mixture: safe withthe maximum charge of 16 cartridges in the angle-shot mortar.

Example 2 Nitroglycerine percent 6.3 Nitroglycol do 4.2 Argillaceousearth do 0.5 Sodium nitrate, 80% finer than 0.1 mm. do 54.6

Ammonium chloride, 80% finer than 0.1 mm.

percent" 34.4

Lead block expansion cc 81 Detonation transmission with a cartridgediameter of 32 mm. cm 2 Safety against methane-air mixture: safe withthe maximum charge of 16 cartridges in the angle-shot mortar.

This principle is applicable not only to the firedamp explosives ofclass III, but also to explosives of the other classes, as follows:

We claim:

1. An improved, high power, firedamp-proof explosive composition,consisting essentially of a major proportion in the range from about 51%to about 56.8% of a mixture consisting of a finely disintegrated alkalinitrate powder having grain diameters below 0.1 mm. to the extent of atleast 20% and at most 90% of said nitrate I powder, and a minorproportion in the range from about 32% to about 35.7% of ammoniumchloride powder in a similarly finely disintegrated stage with graindiameters varying in the same range as those of said alkali nitrate, andfrom 7 to 12% by weight based on said explosive composition of anexplosive sensitizing agent selected from the group consisting of theexplosive materials nitroglyeerine, nitroglycol, diglycol dinitrate,dinitrochlorhydrin. nitropentaerythritol, and any mixture of theseexplosive materials.

2. An improved high-power, firedamp-proof explosive compositionconsisting essentially of a major proportion in the range from about 51%to about 56.8% of a salt mixture consisting of sodium nitrate powderhaving grain diameters below 0.1 mm. to the extent of at least 20% andat most 90% of said nitrate powder, and a minor proportion in the rangefrom about 32% to about 35.7%.

of ammonium chloride powder in a similarly finely disintegrated statehaving grain diameters varying in the same range as those of saidnitrate powder, and from 7 to 12% by weight based on said explosivecomposition of an explosive sensitizing agent selected from the groupconsisting of the liquid explosive materials nitroglycerine,nitroglycol, diglycol dinitrate, dinitrochlorhydrin, solid explosivematerials such as nitropentaerythritol and any mixture of said liquidand solid explosive materials.

3. An improved high-power, firedamp-proof explosive compositionconsisting essentially of a major proportion in the range from about 51%to about 56.8% of a mixture consisting of potassium nitrate in a finelydisintegrated state, having grain diameters below 0.1 mm. to the extentof at least 20% and at the most 90% thereof, and a minor proportion inthe range from about 32% to about 35.7% of ammonium chloride in asimilarly finely disintegrated state, with grain diameters varying inthe same range as those of said nitrate, and between 7 and 12% by weightbased on said explosive composition of an explosive sensitizing agentselected from the group consisting of the liquid explosive compoundsnitroglycerine, nitroglycol, diglycol dinitrate, dinitrochlorhydrin, andsolid explosive compounds such as nitropentaerythritol, and any mixtureof said liquid and solid explosive compounds.

4. An improved high-power, firedamp-proof explosive composition,consisting essentially of a major proportion in the range from about 51%to about 56.8% of a mixture consisting of alkali nitrate which isselected from the group consisting of sodium and potassium nitrate andmixtures thereof, and is finely disintegrated to possess grain diametersbelow 0.1 mm. to the extent of at least 20% and at most 90% thereof,together with a minor proportion in the range from about 32% to about35.7% ammonium chloride ina similarly finely disintegrated state, andcomprising between 7 and 12% by weight based on said explosivecomposition of an explosive sensitizing agent selected from the groupconsisting of nitroglycerine, nitroglycol and mixtures of the lattercompounds in any proportions.

5. An improved high-power, firedamp-proof explosive compositionconsisting essentially of about 4.2% of nitroglycerine, about 2.8% ofnitroglycol, about 56.8% of powdered sodium nitrate having graindiameters smaller than 0.1 mm. to the extent of about 32%, and 35.7% ofpowdered ammonium chloride having grain diameters smaller than 0.1 mm.to the extent of about 22%.

6. An improved high-power, firedamp-proof explosive compositionconsisting essentially of about 6.3% of nitroglycerine, about 4.2% ofnitroglycol, about 54.6% of powdered sodium-nitrate having graindiameters smaller than 0.1 mm. to the extent of about thereof, and about34.4% of powdered ammonium chloride having grain diameters smaller than0.1 mm. to the extent of about 80% thereof.

7. An improved high-power, firedamp-proof explosive compositionconsisting essentially of about 7.5% of nitroglycerine, about 5% ofnitroglycol, about 51% of powdered potassium nitrate having graindiameters smaller than 0.1 mm. to the extent of about 80% thereof, andabout 32% of powdered ammonium chloride having grain diameters smallerthan 0.1 mm. to the extent of about 80% thereof.

8. In a blasting cartridge, an improved high-power, firedamp-proofexplosive composition consisting essential-1y of a major proportion inthe range from about 51% to about 5 6.8% of a mixture consisting of analkali nitrate in a finely disintegrated state with grain diametersbelow 0.1 mm. to the extent of at least 20% thereof and at most thereof,and a minor proportion in the range from about 32% to about 35.7%ammonium chloride in a similarly finely disintegrated state, with graindiameters varying in the same range as those of said alkali nitrate, andcom-prising between 7 and 12% by weight based on said explosivecomposition of a liquid explosive sensitizing agent selected from thegroup consisting of the explosive compounds nitroglycerine, nitroglycol,diglycol dinitrate, dinitrochlorhydrin, and any mixture of saidexplosive compounds. a

9. In a blasting cartridge, a firedamp-proof blasting explosivecomposition with a high explosive power, consisting essentially of amajor proportion in the range from about 51% to about 56.8% of a mixtureconsisting of an alkali nitrate in a finely disintegrated state withgrain diameters below 0.1 mm. to the extent of at least alkali nitrate,and comprising between 7 and 12% byv weight based on said explosivecomposition of a solid explosive sensitizing agent such asnitropentaerythritol.

References Cited in the file of this patent UNITED STATES PATENTSDavidson June 1, 1954 Davidson et a1. June 1, 1954

1. AN IMPROVED, HIGH-POWER, FIREDAMP-PROOF EXPLOSIVE COMPOSTION,CONSISTING ESSENTIALLY OF A MAJOR PROPORTION IN THE RANGE FROM ABOUT 51%TO ABOUT 56.8% OF A MIXTURE CONSISTING OF A FINELY DISINTEGRATED ALKALINITRATE POWDER HAVING GRAIN DIAMETERS BELOW 0.1 MM. TO THE EXTENT OF ATLEAST 20% AND AT MOST 90% OF SAID NITRATE POWDERM AND A MINOR PROPORTIONIN THE RANGE FROM ABOUT 32% TO ABOUT 35.7% OF AMMONIUM CHLORIDE POWDERIN A SIMILARLY FINELY DISINTEGRATED STAGE WITH GRAIN DIAMETERS VARYINGIN THE SAME RANGE AS THOSE OF SAID ALKALI NITRATE, AND FROM 7 TO 12% BYWEIGHT BASED ON SAID EXPLOSIVE COMPOSITION OF AN EXPLOSIVE SENSITIZINGAGENT SELECTED FROM THE GROUP CONSISTING OF THE EXPLOSIVE MATERIALSNITROGLYCERINE, NITROGLYCOL, DIGLYCOL DINITRATE, DINITROCHLORHYDRIN,NITROPENTAERYTHRITOL, AND ANY MIXTURE OF THESE EXPLOSIVE MATERIALS.